1. Field of the Invention
The present invention relates to systems for monitoring vehicle velocities. More particularly, the invention relates to systems monitoring vehicle velocities using scanning light detection and ranging.
2. Description of the Related Art
Traffic control that includes monitoring the velocities of vehicles on the roadways may be implemented by law enforcement officers using various devices and systems, such as Doppler radar and LIDAR. Doppler radar operates in the microwave frequencies, typically X, K, and Ka band, and transmits a continuous or almost continuous wave and measures the speed of vehicles by receiving the reflected signal and using the Doppler principle. Typical Doppler radars can be operated from a stationary point or can be mounted in a law enforcement vehicle and operated while the law enforcement vehicle is moving. They are able to be used in a moving situation because the beamwidth is wide, typically 20 degrees, and therefore do not have to be pointed accurately at the vehicle being measured. But this feature is also a problem because when there are multiple vehicles in the beam, the operator does not know which vehicle is being measured. In the moving mode the Doppler radar subtracts out the speed of the law enforcement vehicle on which it is mounted.
Light detection and ranging (LIDAR) uses a laser pulse and determines the vehicle speed by performing distance time calculations based on the travel time of the reflected light pulse. Because the LIDAR has a very narrow beam, it is very selective of the vehicle being measured even when there are several vehicles within range. But this is also a disadvantage in its usage because the operator must carefully aim the LIDAR at the vehicle, and therefore, it can only effectively be used in stationary applications. The moving application has too much motion to keep it aimed properly.